1. Field of the Invention
The present invention generally relates to a structure of a container base, and more particularly to a base of a container that is repositionable about a hinge in order to partially reduce vacuum pressure experienced by a container during a hot-fill process.
2. Related Art
Conventionally, manufacturers use a hot-fill process to add a product to a container at an elevated temperature, about 82° C., which can be near the glass transition temperature of the plastic material in the plastic container, and then cap the container. As the container and its contents cool, the contents tend to contract and this volumetric change creates a partial vacuum within the container. In the absence of some means for accommodating these internal volumetric and barometric changes, containers tend to deform and/or collapse. For example, a round container can undergo ovalization, or tend to distort and become out of round. Containers of other shapes can become similarly distorted. In addition to these changes that adversely affect the appearance of the container, distortion or deformation can cause the container to lean or become unstable when placed upon a flat surface.
To overcome the partial vacuum within the container created by the hot-fill process, manufacturers have resorted to various different methods to preserve the integrity of the container. In one known method, vertically oriented vacuum panels are formed on the sidewalls of the container. The vacuum panels are adapted to flex inward in response to an internal vacuum to reduce the volume within the container, which lowers the internal vacuum pressure. However, to significantly reduce the vacuum pressure caused by the hot-fill process, these types of vacuum panels are required over a significant portion of the container and are considered by some to be visually unappealing.
Another known method to compensate for internal vacuum pressure is by forming patterned structures on the container. A region of the container having patterned structure of multiple shapes, curves, and bends increases rigidity of the plastic at the region. However, adding these types of patterned structure is required over a significant portion of the container in order to preserve the structural integrity of the container caused by the volumetric changes in the hot-fill process. Patterned structures also add to the amount of plastic within the container, which adds to the weight, and ultimately to the cost.
What is needed is an improved container that overcomes shortcomings of conventional solutions.